1. Field of the Invention
This invention relates generally to a condenser system for controlling humidity of treatable air while maintaining constant temperature and, more particularly, it relates to a microporous membrane positioned between treatable air or other vapor mixtures and a cold water/air interface allowing mass transfer between the treatable air or other vapor mixtures and the interface while hindering heat transfer between the treatable air or other vapor mixtures and the interface.
2. Description of the Prior Art
In the past, most climate control systems have attempted to control both air temperature and water vapor content. But, since air temperature and water vapor capacity are linked, the air temperature and the water vapor capacity are usually are not controlled independently. Instead, temperature is first adjusted (reduced) to achieve the desired water vapor content and then adjusted (increased) to reach the desired final temperature. Adjusting the temperature twice requires additional energy and reduces efficiency of the dehumidifier.
For instance, in the prior art climate control members, to change the humidity of air (e.g., changing the amount of water vapor in the air) without altering the temperature, two or more unit operations were necessary. For example, in order to alter eighty (80%) percent relative humidity air at twenty-five (25.degree. C.) degrees Celsius to seventy (70%) percent relative humidity air at twenty-five (25.degree. C.) degrees Celsius, at least the three following steps were required:
1. Cool the air to nineteen (19.degree. C.) degrees Celsius; PA1 2. Separate the condensed water from the bulk air which would be at one-hundred (100%) percent relative humidity; and PA1 3. Heat the remaining bulk air from nineteen (19.degree. C.) degrees Celsius to twenty-five (25.degree. C.) degrees Celsius. PA1 1. Pressurize the air with a compressor unit operation; and PA1 2. Pass the pressurized air through a water vapor selective membrane.
Step 3 from the above conventional process represents the inherent overall process inefficiency since the energy required to reheat the bulk air is in addition to the energy used to initially cool the air in Step 1. Thermodynamically, the overall energy expended in the process is always greater than latent heat of condensation requirements.
In the art, an alternative process currently used for some industrial applications is as follows:
The above-described conventional process is only practical for some industrial applications where the end use of the air is at high pressures. The pressurizing process would be too costly to adapt to ambient pressure uses of air such as air conditioning for buildings and the like or other enclosed environments environmental controls.
In order to overcome the inherent shortcomings of the above processes, there have been attempts in the prior art using porous membranes to stabilize the cold water/air interface. Unfortunately, however, the conventional membrane systems do not actually insulate the process of mass transfer from heat transfer. In fact, there is a strong interrelationship between changes in humidity and temperature during the operation of the conventional membrane-based humidity control processes in the prior art.
Another conventional membrane process includes a process called "membrane-gap distillation". In the membrane-gap distillation process, a vapor gap placed between a multiple component "hot" liquid phase and a condensing "cold" surface increases the thermal efficiency of the membrane-gap distillation processes. The membrane-gap distillation process, however, changes the ratio of the components in a liquid mixture via vaporization followed by condensation. Therefore, the membrane-gap distillation process is for changing the relative concentrations of the liquid compounds and not the changing of relative concentrations of the vapor compounds which is dehumidification.
Accordingly, there exists a need for an apparatus and method for changing humidity while maintaining constant temperature. Additionally, a need exists for an apparatus and method which utilizes a membrane to change the humidity of air while maintaining a constant temperature. Furthermore, there exists a need for an apparatus and method which positions a microporous membrane between treatable air and a cold water/air interface allowing mass transfer between the treatable air and the interface while hindering heat transfer between the treatable air and the interface.